Avatto curtain switch: change main entity to select.

cover entity requires some feedback about curtain position.  Without it, Home
Assistant considers the whole entity to be unavailable.  Instead, implement
as a select entity.

Issue #292

custom_components/tuya_local/devices/avatto_curtain_switch.yaml

@@ -1,18 +1,18 @@
 name: Avatto curtain switch
 primary_entity:
-  entity: cover
-  class: curtain
+  entity: select
+  icon: "mdi:curtains"
   dps:
     - id: 1
-      name: control
+      name: option
       type: string
       mapping:
         - dps_val: open
-          value: open
+          value: Open
         - dps_val: close
-          value: close
+          value: Close
         - dps_val: stop
-          value: stop
+          value: Stop
 secondary_entities:
   - entity: light
     category: config